Reliable detection of defects in shiny manufactured parts, such as the converted ends of beverage cans, has been difficult. In particular, there is a need to improve detection of scrap-in-die defects in converted-end inspection. Scrap-in-die defects are small dents caused by the accidental presence of metal fragments (“scrap”) in the conversion press when a beverage shell is stamped (“converted”) into a converted end. Such defects are critical, since they can cause leaks, and are often difficult to detect.
Various techniques have been tried to detect such defects. For example, acquiring multiple images of a part to be inspected under different illumination geometries to deduce three-dimensional structure has been tried. However, the particular techniques tried up to this point have not been very impressive.
Further limitations and disadvantages of conventional, traditional, and proposed approaches will become apparent to one of skill in the art, through comparison of such systems and methods with the present invention as set forth in the remainder of the present application with reference to the drawings.